I. Field of the Invention
This invention relates to a valve used in oil field pumps for cementing, fracturizing and acidizing operations and, in particular, to a valve adapted to sealing cooperate with a valve seat having a hardened alloy valve head with urethane legs replaceably connected to the valve head in order to reduce the operating mass of the valve thereby increasing productive life.
II. Description of the Prior Art
Pumps and other valving mechanisms are widely used in deep well drilling and production operations. The valve assemblies associated with such devices can be subjected to extreme stresses as the valve pumps several hundred strokes per minute. In addition, the pump may be used in cementing, fracturing or acidizing operations subjecting the valve to an errosive environment. To prevent frequent downtime in the production well, the pump, particularly the valves, must be rugged enough to withstand such an environment yet capable of extreme stroke rates.
Past known valve assemblies used in oilfield application employed one or two piece hardened metal alloy valves which cooperated with a valve seat. The two-piece valve included a valve cap threadably mounted to a valve body having guide legs. A rubber or polyurethane insert ring is mounted between the cap and body to provide sealing engagement between the valve and the valve seat. The one-piece valve includes an integral valve cap and body to which the valve insert is mounted. Although these valves can be removed to replace the sealing insert or the entire valve, such downtime can be costly and is therefore preferably minimized.
The striking shock of the past known valves results in failure of the valve. The high stroke rate in conjunction with the mass of the valve results in erosion and failure of the valve, the sealing valve insert and also the operating mechanisms associated with the valve. The weight of the metal valve limits the stroke rate yet the valve must be resistant to the wear caused by the pumping fluids and the high shock loads associated with the pumping. Moreover, in the event of damage to the guide legs the entire valve must be replaced. Accordingly, the guide legs are made thicker to reduce breakage thereby further increasing the weight of the valve. All of these factors limit the effectiveness and operating life of the past known valve assemblies.